1. Field of the Invention
This invention relates to a polyamide hotmelt adhesive containing fillers and to its use.
2. Discussion of Related Art
Polyamide hotmelt adhesives containing fillers are known. Thus, DE 23 61 486 describes a hotmelt adhesive consisting of a polyamide resin and 5 to 80% by weight of an inorganic filler. The polyamide resin is produced from 0.5 to 0.8 equivalent of a polymeric fatty acid, 0.2 to 0.5 equivalent of another dicarboxylic acid, 0 to 0.6 equivalent of ethylenediamine and 0.4 to 1.0 equivalent of piperazine, the equivalent ratios between the dicarboxylic acids and the diamines being substantially the same. The five Examples only describe polyamides of which the acid value is greater than the amine value by at least 2 units. Chalk and heavy spar are mentioned as inorganic fillers (cf. the Examples and page 2, paragraph 4). The polyamide hotmelt adhesive is said to be used as an edge-banding glue for heat-resistant edge glueing. The edge veneer materials mentioned include veneers of wood, melamine/formaldehyde or urea/formaldehyde resins, polyesters and also polyvinyl chloride and polyacrylonitrile/butadiene/styrene. These edge veneer materials are bonded to furniture boards.
Polyamide hotmelt adhesives containing fillers are also known from Schering AG's pamphlet on "Eurelon". Among the 15 types mentioned, there is one of which the amine value is higher than acid value. All the other types either have substantially the same values or a higher acid value. Inorganic fillers, such as chalk, heavy spar, kaolin or aluminium oxide, may be added to these polyamide resins in their molten form. In view of the relatively low melt viscosity of some of the resins, preference should be given to light fillers with little or no tendency to sediment in order as far as possible to avoid sedimentation of the filler during application of the hotmelt adhesive. The incorporation of fillers is recommended if, in the bonding of porous materials, an overly thin adhesive penetrates into the substrate to such an extent that the actual glueline consists solely of a paper-thin film. Not only do the surfaces to be bonded have to be degreased, it is also necessary in most cases, for example in the case of metals, to remove troublesome oxide or scale layers by mechanical roughening or pickling or, in the case of plastics with non-polar surfaces, to convert these surfaces into a polar state by a chemical pretreatment. The following materials may be bonded: aluminium and aluminium alloys, steel and stainless steel, magnesium and magnesium alloys, ceramic materials, glass and china, concrete and asbestos cement, polyethylene, polypropylene, polyamides, foams, leather and rubber, natural and synthetic rubber and various materials, such as thermosets, rigid PVC, polystyrene, polyacrylates, polycarbonates and polyacetates. The hotmelt adhesives are used not only in the shoe industry, the furniture industry, the automotive industry and the packaging industry, but also in the electrical industry, inter alia for bonding coil ends and coil windings, in the bonding of housings and in the application of ornamental trims, etc.
DE 42 11 125 describes polyamide hotmelt adhesives which may contain 0.5 to 2% by weight of fillers. Particulars of the type of fillers used are not provided. The polyamides may be both acid-terminated and amine-terminated. Amine-terminated polyamides are used in the Examples. The hotmelt adhesives are used to bond non-pretreated polyethylene and polyvinyl chloride or metals, more particularly copper, lead and aluminium, to one another or to themselves. Specific applications are in the electrical industry, more particularly for bonding cables and lines.